Project Summary/Abstract: Supplement for Mimicry of Amyloid Oligomers Amyloid oligomers are now thought to be the damaging molecular species in Alzheimer's disease, Parkinson's disease, and many other amyloid diseases. Understanding the structures of these oligomers is essential to understanding their mechanism of action, and quite possibly to developing drugs to prevent or treat these diseases. Studying the structures of the oligomers at high resolution is challenging, because the oligomers are heterogeneous and dynamic, forming a variety of sizes and structures that can interconvert. Thus far, there are no atomic-resolution structures of oligomers of the beta-amyloid peptide, Abeta, the 40- or 42-amino acid polypeptide closely associated with Alzheimer's disease. Grant GM097562 aims to determine the structures of oligomers formed by Abeta by incorporating key fragments of Abeta into macrocyclic beta-sheet peptides designed to mimic the key beta-hairpin building blocks that are thought to make up Abeta oligomers. The PI has determined X-ray crystallographic structures at atomic resolution of trimers formed macrocyclic beta-sheet peptides containing fragments from the central and the C-terminal regions of Abeta. Grant GM097562 aims to build on the discovery of these trimers and the higher-order oligomeric assemblies that they form. The broad overarching goal is to understand the relationship between the atomic-resolution structures of the oligomers and their biological and biophysical properties. To achieve these goals, the PI will synthesize macrocyclic beta-sheet peptides that incorporate different aspects of Abeta structure, determine the X-ray crystallographic structures of the oligomers that these peptides form, measure their cytotoxicity, elucidate their mechanisms of cytotoxicity, and correlate their cytotoxicity and their crystallographic structure by means of biophysical studies of their solution-phase properties. In the course of these studies, an unanticipated opportunity to accelerate our research has emerged. Successful advances toward Specific Aim 2 of Grant GM097562 have allowed us to significantly increase the size of our peptide targets. The synthesis of these peptides allows us to more closely mimic Abeta oligomers. The synthesis of these peptides is important because we can use them as tools to study the biophysical and biological properties of oligomers in Alzheimers? disease. We synthesize these peptides with an automated microwave peptide synthesizer. Synthesis of these peptides is limited by the instrument?s availability; the instrument belongs to another laboratory and is in frequent need of repair, delaying our research. Recently, the instrument manufacturer has announced that they are ending hardware support, ending the possibility of future repairs. Obtaining our own automated microwave peptide synthesizer will accelerate the research by allowing for the rapid and efficient synthesis of elongated peptides on a day-to-day basis, without delays.